Sabot



March 4, 1969 l. R. BARR 3,

' SABOT Filed May 25, 1967 Irwin R. Barr F I G 3 INVENTOR ATTORNEY United States Patent ()1 ice 3,430,571 Patented Mar. 4, 1969 4 Claims ABSTRACT OF THE DISCLOSURE A sabot is disclosed having a cylindrical portion adapted to position the sabot in a gun barrel, an axial bore containing a projectile, and a frusto-conical portion having a plurality of longitudinal slots extending radially from the interior of the sabot to the exterior surface thereby forming a plurality of wedge-shaped segments which are covered by a frusto-conical sleeve of flexible material. As a high pressure gas propels the sabot and projectile through the gun barrel, the gas exerts a force on the flexible frusto-conical sleeve covering which transmits a force through the wedge-shaped segments to the projectile so as to create a frictional force between the bore of the sabot and the surface of the projectile which is suflicient to prevent a relative axial movement between the sabot and the projectile.

This invention relates to sabots used for producing high muzzle velocities in projectiles, and more particularly to a sabot adapted to constrict around and frictionally grip the projectile as it travels through the gun barrel so that it is not necessary to provide positive locking means to fasten the sabot to the projectile, thus providing a clean aerodynamic surface when the sabot is removed upon the projectile leaving the gun barrel.

It is well known that the velocity imparted to a projectile being propelled through a gun barrel may be increased by providing a relatively lightweight body of large diameter having an axial bore, and commonly known as a sabot, into which a relatively heavy projectile is inserted to increase the area on which the propelling gas pressure acts so as to increase the total force propelling the projectile through the gun barrel. In prior US. Patent No. 2,939,395, a sabot is constructed of a resilient material, such as plastic or fiber glass, and utilizes the propelling gas pressure in the gun barrel to constrict a portion of the sabot around the projectile to create a frictional force between the axial bore of the sabot and the surface of a finned cylindrical projectile that enables the sabot to pull the projectile through the gun barrel. Upon leaving the gun barrel, the pressure is removed, which in turn removes the frictional force between the sabot and the projectile to enable the sabot to be removed from the projectile.

However, oftentimes the constriction of the resilient sabot is resisted by the lateral and other compressive forces in the material to such an extent that the frictional force exerted by the bore of the sabot against the surface of the projectile is insutficient to prevent a relative axial movement between the sabot and the projectile, thus reducing the propelling force transferred from the sabot to the projectile and consequently the velocity imparted to the projectile. This is much more apt to occur as the sabot approaches the muzzle of the gun barrel, because the pressure exerted on the sabot by the propelling gas is greatly reduced as the sabot travels through the barrel. Although it is sometimes possible to extend the length of the frusto-conical portion of the sabot so that the axial bore of the sabot engages a greater surface area of the projectile and thus increases the frictional force between the sabot and the projectile, this is not always desirable because the increased volume of the sabot reduces the amount of propellant which can be contained in a cartridge of a given size and accordingly reduces the amount of the propelling gas pressure created by the ignition of the propellant.

Accordingly, it is a feature of the present invention to provide an improved sabot constructed from a resilient material which substantially reduces the lateral and other compressive forces in the constricted portion of the sabot, yet enables the propelling gas to exert a maximum force against the projectile so as to create a frictional force between the bore of the sabot and the surface of the projectile which is sufficient to prevent a relative axial movement between the sabot and the projectile.

In the present invention, the sabot has a frusto-conical portion adapted to be constricted, with partial longitudinal slots extending radially from an annular connecting web portion about the bore at the interior of the sabot to the exterior surface of the frusto-conical portion so as to form wedge-shaped segments and relieve the compressi've forces in the frusto-conical portion of the sabot. The frusto-conical portion of the sabot is covered with a frusto-conical sleeve of flexible material to prevent the propelling gas from entering the longitudinal slots and cause it to exert a maximum effective force through the sleeve, wedge-shaped segments, and annular inner web, to the projectile so as to create a frictional force between the bore of the sabot and the surface of the projectile which is suflicient to prevent a relative axial movement between the sabot and the projectile, and thus enable the sabot to impart a maximum propelling force to the projectile.

Still other objects, features, and attendant advantages will become apparent to those skilled in the art from a reading of the following detailed description of the embodiment constructed in accordance with the invention, taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a cross-sectional View showing a projectile and a sabotaccording to this invention being propelled through the bore of a gun barrel.

FIG. 2 is an exploded perspective view of an embodiment of the sabot of FIG. 1.

FIG. 3 is a sectional view of the sabot of FIGS. 1 and 2, taken along the section line 33 of FIG. 1, showing how the force exerted by the propelling gas pressure against the surface of the flexible, frusto-conical sleeve covering the wedge-shaped segments is transmitted to the projectile so as to create the desired frictional force between the bore of the sabot and the surface of the projectile.

Referring now in detail to the figures of the drawing, in FIG. 1 is shown a relatively lightweight sabot, generally indicated at 11, being propelled through the bore 13 of a gun barrel 15 by a high pressure gas and having an axial bore 17 containing a relatively heavy, sharp pointed projectile 19, having straight or canted stabilizing fins at the rearward end that is long with respect to its crosssectional area so as to increase its mass/cross-sectional area ratio and thus give it increased penetrating power for any given velocity. The sabot 11 may suitably be formed of constrictable materials such as a mixture of fiber glass reinforced plastic or light metals, for example, aluminum or magnesium, and has a large diameter cylindrical portion 21 which positions the finned projectile 19 in generally co-axial alignment with the gun barrel 15 and engages the bore 13 in a sealing fit so as to prevent the propelling gas from leaking around the sabot 11 and thus enabling it to impart a maximum velocity to the projectile 19. Although the sabot 11 herein disclosed is especially useful with the illustrated type of projectile 19, it is to be understood that a sabot 11 constructed in accordance with this invention may be used with other types of projectiles.

The sabot 11 has a frusto-conical pOrtiOn 23 extending rearwardly from the cylindrical portion 21 which is adapted to constrict around the projectile 19 and create a frictional force between the axial bore 17 of the sabot 11 and the surface of the projectile .19 so as to prevent relative axial movement between the sabot 11 and the projectile 19. The frusto-conical portion 23 has a plurality of longitudinal slots 25 extending radially from an interior annular projectile-engaging web 26 to the surface of the conical portion 23 of the sabot 11 so as to form a plurality of apex-connected wedge-shaped Segments 27. Covering the wedge-shaped segments 27 of the frustoconical portion 23 of the sabot 11 is a frusto-conical sleeve, generally indicated at 29, of flexible material, such as a non-reinforced plastic, for example nylon or polyethylene, which provides a surface 3.1 for the propelling high pressure gas to act directly upon and prevents the gas from entering the longitudinal slots 25.

When a high pressure :gas is created rearward of the sabot 11, it exerts a force normal to the surface 31 of the flexible frusto-conical sleeve 29 which may be considered to have two components, one of which acts parallel to the axis of the bore 13 of the gun barrel 15 so as to propel the sabot 11 through the barrel, and the other of which acts perpendicularly to the axis of the bore 13 of the barrel 15 to constrict the wedge-shaped segments 27 of the frusto-conical portion 23 and create a frictional force between the axial bore 17 and the surface of the projectile 19 to enable the sabot 1 1 to pull the projectile '19 through the gun barrel 15.

When the high pressure gas exerts a force normal to the surface 31 of the flexible frusto-conical sleeve 29 it will tend to press the flexible sleeve, to some extent, into the radially extending longitudinal slots 25 in the frustoconical portion 23 of the sabot 11, as indicated by the depressions 33. However, the sleeve 29 resists, to some extent, the force exerted by the high pressure gas, the sleeve being only partially extruded into the slots, and substantially the total radial force applied to the sleeve 29 is transmitted to and through the segments 27. As a result, the force transmitted through each wedge-shaped segment 27 to the rojectile 19 is approximately equal to the product of the gas pressure and the effective arcuate area of the flexible sleeve encompassing the exterior surface of a wedge-shaped segment 27 and a slot 25, the sum total force transmitted through the wedge-shaped segments 27 to the projectile being approximately equal to the product of the initial interior area of the sleeve 29 and the gas pressure exerted thereon.

If the flexible frusto-conical sleeve 29 were not used to cover the wedge-shaped segments 27 of the frustoconical portion 23 of the sabot 11, then the high pressure gas would enter the radially extending longitudinal slots 25 and exert a force normal to the radial surfaces of the wedge-shaped segments 27 which would result in a resolution of forces having a radial outward vector component which would oppose and thereby decrease the magnitude of the perpendicular component of the force exerted on the segment by the propelling gas, and a cross-wise component which would compress the wedge-shaped segments 27 so as to decrease the exterior surface area over which the propelling gas acts, and thereby further diminish the perpendicular forces applied to the projectile 19 and result in a decreased frictional force between the axial bore '17 of the sabot 11 and the surface of the projectile 19 which would tend to cause a relative axial movement between the sabot 11 and the projectile 19.

While the invention has been illustrated and described with respect to a single preferred embodiment, it will be apparent to those skilled in the art that still other embodiments are possible and that various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, instead of a -frusto-conical sleeve being used to cover the wedgeshaped segments of the frusto-conical portion of the sabot, a plurality of arcuate segments arranged in a generally frusto-conical shape and integrally connected at the narrow end could be used to cover the longitudinal slots between the wedge-shaped segments and thus enable the propelling force to be exerted over a surface area having approximately the same effective annular dimensions as that provided by the unitary frusto-conical sleeve. Accordingly, it is to be understood that the invention is not to be limited by the illustrated embodiment, but only by the scope of the appended claims.

That what is claimed is:

1. In a sabot arrangement adapted to engage the bore of a barrel and including a sabot of constrictible material, a bore formed in said sabot for carrying a smooth cylindrical surfaced projectile, and a rearward portion adapted to be radially constricted and exert a frictional projectileretaining force through the wall surface forming said bore in response to propellant gas pressure applied to the exterior surface of the rearward portion of the sabot in propelling the sabot through the bore of a barrel, the improvement comprising:

wedge-shaped segments formed in the rearward section of said sabot and defining therebetween longitudinal siots o reduce the circumferential compressive forces developed in said segments due to the constriction of the rearward portion,

said segments being integrally circu-mferentially joined adjacent and along their smaller radially inner ends, and

an arcuate circumferentially continuous cover externally encompassing and covering each slot for the propelling forces to act upon.

2. In a sabot arrangement according to claim 1, the

improvement further comprising:

a cylindrically smooth surfaced projectile disposed and carried within the bOre of said sabot, the radial constriction of said sabot eflecting a friction force to enable the sabot to pull the projectile through the bore of the barrel.

3. In a sabot arrangement according to claim 1, the

improvement further comprising:

the portion of said sabot adapted to engage the bore of a barrel being cylindrical and engaging the barrel bore in a gas-sealing fit,

said rearward portion being frusto-conically shaped and extending rearwardly from said cylindrical portion,

the integrally circumferentially joined inner smaller end surfaces of said wedge-shaped segments forming said projectile-carrying sabot bore as a smooth continuous annular band, said slots extending longitudinally along a substantial portion of said projectilecarrying sabot bore, and

said arcuate cover being formed of a resilient material and having a frusto-conical shape encompassing the longitudinal and radially extending slots of the frustoconical portion of the sabot to effect sealing of said slots and provide a continuous tapered surface upon which a propelling force can act.

4. In a sabot arrangement according to claim 3, the improvement further comprising:

said projectile having a smooth cylindrical body portion with a tapered nose end and a plurality of fins formed at the rearward end, and said projectile being relatively heavy as compared to said sabot,

said projectile nose and a substantial extent of said smooth cylindrical body portion extending into said sabot bore.

References Cited UNITED STATES PATENTS 2,939,395 6/ 1960 Barr 102--93 3,000,316 9/ 1961 Dunlap et a1. 102-93 3,107,615 10/1963 Brady l02'93 X 3,125,957 3/ 1964 Lipinski 102-93 ROBERT F. STAHL, Primary Examiner. 

